Lawrence Mak

Ship performance monitoring and analysis to improve fuel efficiency

A pilot project was launched to monitor vessel performance and to explore ways to reduce fuel consumption. A prototype Vessel Performance Monitoring and Analysis System (VPMAS) was used to collect information over a three week period. The project objective was to collect needed data, conduct preliminary analysis to establish trends, explore key performance indicators (KPI) to establish baseline, and explore data products for performance management. Performance management includes improving vessel performance and supporting efficient operation to reduce fuel consumption. For the pilot project, only a subset of vessel performance data was collected. Current key performance indicators (KPIs) include fuel consumption per trip, fuel consumption per distance travelled, fuel consumption per displacement distance and fuel consumption per payload distance. The dataset will expand in the future and will include the effect of environmental conditions. Preliminary analysis includes comparing the normal route for calm sea states and irregular routes taken probably to avoid heavy sea states; assessing the maneuvers in and out of harbors, computing key performance indicators, assessing the data trends and general statistics, and identifying data products to support performance management. Initial results show that automatic fuel measurement was in good agreement with manual tank sounding. A voyage on an irregular route consumed almost twice the amount of fuel consumed in a normal route. Fuel consumption would be reduced if constant speed is used in open water and if deviations from the desired routes could be minimized, for example, through optimized autopilot.

Assessment of Thermal Protection of Life Rafts in Passenger Vessel Abandonment Situations

Inflatable life rafts are currently used on almost all passenger, fishing and commercial vessels, and offshore oil installations. Worldwide, life rafts are the primary evacuation system from fishing vessels with relatively small crews to large Roll on/Roll off passenger vessels with over a thousand passengers and crew. While International Maritime Organization (IMO) standards currently require inflatable life raft components to “provide insulation” or “be sufficiently insulated”, there are no performance criteria for these requirements (IMO, 1996). In a passenger ship abandonment situation in cold water, passengers may be wearing very little personal protective clothing. Therefore, life rafts provide the only significant thermal protection against the cold ocean environment while they await rescue. Manufacturers equip life rafts with an insulated floor to reduce heat loss from direct contact with the cold ocean water. The insulation provided is critically important for life raft occupants who have little protective clothing. The heat loss of unprotected persons is drastically increased if there is a layer of water on the floor as would likely be the case when someone climbs into the life raft from the ocean or if water is splashed into the life raft in heavy weather. Experiments were conducted in mild cold (16oC water temperature and 19oC air temperature) and cold conditions (5oC water temperature and 5oC air temperature) to assess the thermal protection of a 16-person, Safety of Life at Sea (SOLAS) approved, commercially available life raft. This paper presents results in the mild cold condition only. It has been found that the wave height effect may be ignored as a first approximation to reduce the number of environmental variables because the results demonstrated that wave height effect is less important with leeway. Heat conductance decreases considerably with floor inflation. Heat conductance is about the same with floor inflated 50% and 100%. The CO2 concentration in the 11-person test exceeded 5000 ppm in less than an hour inside the life raft, with closed canopy and no active ventilation. This hostile microclimate inside the life raft suggests that active ventilation at a known rate is required to keep the CO2 level at a safe controlled level when longer duration tests are to be conducted in the future. Wet clothing has a significant effect on occupant heat loss.

Behavior of the Residual Wave Components in a 3D Wave Basin After the Termination of the Wave Maker

After the termination of the wave making, the characteristics of the existing wave components in a 3D large scale Offshore Engineering wave Basin (OEB) at the National Research Council of Canada have been investigated experimentally. In the generation of any wave in the tank we get the relevant primary wave components along with bounded wave components if the incident primary wave has more than one frequency. Inevitably we also get interacted wave components, natural frequency components of the tank and other free waves. In this paper the tank’s natural frequency components, bounded wave components and other free waves after the termination of wave making were investigated using several cases of mono- and bi-chromatic waves. These component energies were then compared with the total energy of the measured primary waves. The magnitudes of the residual undulations are also investigated for mono-, bi- and multi-chromatic waves over different time segments. Several sets of wave data are analysed to perceive the energy due to natural frequency of the basin, energy transferred to the side bands and the damping rate of the residual waves in the tank with respect to the chosen incident wave conditions. In the analysis it is observed that the energy damping rate varies with the incident wave condition but seems much faster than that of 20 minutes traditional waiting time in between two runs in the OEB. The energies for tank’s natural frequency components and other free waves were found to be very small compare to the incident primary wave energies.Copyright

Vessel Performance Analysis and Fuel Management

A prototype Vessel Performance Monitoring and Analysis System (VPMAS) was deployed on a ferry to acquire needed performance data, to help improve vessel performance and reduce fuel consumption. A paper published in 2014 described preliminary data trends observed, key performance indicators computed, data products explored and exploratory tools developed for crews to gain insight into their vessel operation. The current paper describes further analysis of the operational data for speed optimization in calm sea states and the preliminary development of trim optimization software.It was found that trip durations around 7 hours (13.3 knots) use the least amount of fuel. The least amount of fuel is used when the excess distance travelled is minimized and the voyage time is optimized. There is a lot of leeway in terms of voyage time and excess distance travel by the ship before there is a heavy penalty on fuel consumption. Considering only a mean draft of 6 m and an average speed of 14 knots in the current paper, the optimal trim condition for the ferry is around −0.6 m (bow down), which reduces the resistance by 15% compared to the even keel condition. Positive trim causes the considerable increase of the total resistance consistently.Copyright

Thermal Requirements for Surviving a Mass Rescue Incident in the Arctic: Preliminary Results

Maritime and air traffic through the Arctic has increased in recent years. Cruise ship and commercial jet liners carry a large number of passengers. With increased traffic, there is a higher probability that a major disaster could occur. Cruise ship and plane accidents could be catastrophic and may require mass rescue. Due to the remote location, limited search and rescue resources, time for these resources to get to the accident location and large number of survivors, the retrieval time could be several days. Therefore, survivors may be required to survive on their own for days while they await rescue. Recognizing that the International Maritime Organization does not have specific thermal performance criteria for liferafts and lifeboats and personal and group survival kits, the Maritime and Arctic Survival Scientific and Engineering Research Team (MASSERT) initiated a research project to improve safety and provide input for advances to regulations. The objective of the project is to investigate if the current thermal protective equipment and preparedness available to people traveling in the Canadian Arctic are adequate for surviving a major air or cruise ship disaster and to identify the minimum thermal protection criteria for survival. This project builds on the results and tools developed in other research projects conducted by the team on thermal protection of liferafts, lifeboats and immersion suits. The project is divided into three major phases — clothing ensemble testing with thermal manikins, a physiology experiment on sustainable shivering duration and ensemble testing in Arctic conditions with human subjects. A numerical model uses these data to simulate survival scenarios. In the first phase of this project, the thermal resistance values of the protective clothing typically available to cruise ship and aircraft passengers were measured using two thermal manikins. The ensembles included Cabin Wear, Deck Wear, Expedition Wear, Abandonment Wear and protective clothing from Canada Forces Major Air Disaster Kit (MAJAID). Tests were conducted on dry and wet ensembles at 5°C and −15°C with and without wind. There is very good agreement between the thermal resistances measured by the two manikins. The differences in thermal resistances observed are likely caused by variations in fit and wrinkles and folds in the ensembles from dressing. With no wind, the thermal resistance is lowest with Cabin Wear and highest with MAJAID clothing inside the down-filled casualty bag. The Expedition Wear, the Abandonment Wear and the MAJAID clothing have about the same thermal resistance. With 7 metre-per-second wind, the thermal resistance of all ensembles decreased significantly by 30% to 70%. These results highlight the importance of having a shelter as a windbreak. For wet clothing ensembles at 5°C, the initial wet thermal resistance was 2 to 2.5 times lower than the dry value, and drying times ranged up to 60 hours. This highlights the importance of staying dry. Preliminary predictions from the numerical model show that the survivors in Expedition Wear, even with sleeping bag and tent, can be mildly hypothermic and need to depend heavily on shivering to maintain thermal balance. In a shelter, the predicted metabolic rate is roughly double the resting rate; it is triple the resting rate without protection from the wind. Further research is required to study shivering fatigue and age effects. Research on mass rescue scenarios for cruise ships and airplanes survivors should ideally involve subjects of both genders and the elderly.Copyright

Thermal Protection and Microclimate of SOLAS Approved Lifeboats

Lifeboats are used as an evacuation system on a wide variety of offshore structures and marine vehicles. Currently, International Maritime Organization (IMO) Lifesaving Appliances (LSA) Code does not specify thermal protection and ventilation criteria for lifeboats. A test program was conducted to assess the system thermal protection and microclimate of SOLAS approved lifeboats for the Arctic environment. Some of the research findings of the first phase experiments are reported in this paper. In conducting experiments with a 72-person SOLAS approved lifeboat, the study found that the lifeboat only had a ventilation rate of 2 litres per second with vents open only, which may not be adequate. Inadequate ventilation will result in high concentration of carbon dioxide, causing headache, dizziness, restlessness, breathing difficulty, sweating, and increased heat rate, cardiac output and blood pressure. All of these may adversely affect lifeboat occupants in performing survival tasks. Using a thermal manikin, only slight decrease in thermal resistance (less than 10%) was observed in many test cases, when active ventilation was implemented (ventilation rate of 31 and 42 litres per second) and when side hatches were opened (ventilation rate of 95 litres per second). This suggests that reasonable increase in ventilation rate may be implemented without trading off much in thermal protection. However, a more noticeable decreases in thermal resistance (15% to over 30%) were observed when clothing was wet. This suggests it is critical to stay dry. A mathematical model was also developed to assess heat and cold stress of lifeboat occupants under different environment, lifeboat, occupant and ventilation conditions.Copyright

Experimental Study and Modelling of Thermal Protection in Liferafts Using a Thermal Manikin and Human Subjects

Experiments were conducted in cold conditions (5°C water temperature and 5°C air temperature) to assess the thermal protection of a 16-person, SOLAS approved, commercially available liferaft using a thermal manikin and human subjects. The comparison tests included four cases — 1. Inflated raft floor; dry clothing (Idry ); 2. Inflated raft floor; wet clothing (Iwet ); 3. Uninflated raft floor; dry clothing (Udry ); 4. Uninflated raft floor; wet clothing (Uwet ). The results demonstrated equivalence in insulation between human subjects and a thermal manikin for all cases of comparison (Idry: Manikin 0.236 (m2 °C)/W versus Human 0.224 (m2 °C)/W; Iwet: Manikin 0.146 (m2 °C)/W versus Human 0.145 (m2 °C)/W; Udry: Manikin 0.174 (m2 °C)/W versus Human 0.185 (m2 °C)/W; Uwet: Manikin 0.101 (m2 °C)/W versus Human 0.116 (m2 °C)/W). The results also showed the repeatability of the thermal manikin tests (0.177 (m2 °C)/W versus 0.171 (m2 °C)/W in Udry baseline case; and 0.101 (m2 °C)/W versus 0.104 (m2 °C)/W in Uwet baseline case). The results indicated that the insulation of a closed cell foam floor is comparable to an inflated floor (0.236 (m2 °C)/W compared to 0.221 (m2 °C)/W and 0.236 (m2 °C)/W for closed foam floor from manufacturer A and B respectively). TPA provided considerable additional insulation than all baseline cases. A test with a human subject wearing a TPA in the Uwet case showed an improved insulation of 48% over the baseline case. TPA provided more additional insulation than a wet suit in all test cases except Udry case. In Uwet case, the worst test condition, the insulation obtained by sitting on a lifejacket (0.149 (m2 °C)/W) is less than wearing a TPA (0.158 (m2 °C)/W). Both of these are better than sitting directly on an uninflated floor (0.104 (m2 °C)/W) or a closed cell foam floor (0.129 (m2 °C)/W). There is a significant decrease in insulation value sitting in 10 cm of water (0.05 (m2 °C)/W). Two human subject tests show an insulation value of 0.079 (m2 °C)/W and 0.081 (m2 °C)/W respectively. A liferaft occupant heat loss model was developed and integrated with Defense R&D Canada’s Cold Exposure Survival Model to predict survival time. For Uwet case, the worst test condition, the survival time is 32 hours and functional time is 24 hours for the experimental conditions.© 2009 ASME

An Empirical Method for the Estimation of Towing Resistance of a Life Raft in Various Sea States

Current IMO regulations require life rafts to be tow tested only in calm water. In real evacuation situations, life rafts are deployed in the prevailing environmental conditions, with wind and waves. Added wave resistance is small at low wave heights but increases nonlinearly with increased wave height. If life rafts are to be towed in moderate seas (up to 4 m significant wave height), tow force estimates based only on calm water tow resistance become less reliable. Tow patches, towline, towing craft etc. also need to be designed to withstand dynamic wave loading in addition to mean load. Therefore, mean tow force, tow force variation and maximum tow force are important. A full-scale 16-person, commercially available, SOLAS approved life raft was towed in the tank, in upwind, head seas with significant wave height of 0.5 m. The measured tow force showed that it could be treated as a linear system with wave amplitude, by demonstrating that tow force is mainly inertial and follows a Rayleigh distribution. Therefore, extreme-value statistics used for waves can be applied to developing equations for predicting tow force. A method is proposed to predict life raft tow force at different tow speeds and in various sea states, with waves and wind. The method involved using tank experiments to obtain tow force response for one sea state. The information can then be used to predict life raft tow force in wind and waves for different sea states. Three equations are proposed to demonstrate that a simple tank experiment could provide valuable information necessary to empirically estimate the mean tow force, tow force variation and maximum tow force for a specific life raft in different sea states. The equations are developed for upwind, head seas. These equations were extensively validated using tow force measured in the tank. They were partially validated with limited sea trial data, by towing the same 16-person life raft and a 42-person life raft in upwind, head seas with significant wave height of 1.3 m. The equations were able to predict maximum tow forces to within 15% of the measured.Copyright

Motion Response of a Full-Scale Life Raft in Laboratory Tow Experiments

A 16-person full-scale life raft was towed in a tow tank in calm water, regular and irregular waves. The objectives were to assess the raft motion response, occupant motion, tow force, effect of tow speed, effects of different test variables (drogue deployment, floor inflation, weight distribution and ballast), and the likelihood of occupant motion sickness. Comparisons of RAOs obtained in regular and irregular waves demonstrated that irregular waves could be used as a cost effective means to determine raft response with a high degree of confidence. They also show that the life raft tow performance is different in waves than in calm water. For example, mean tow force is 20% higher in the sea state tested than in calm water. Floor inflation, drogue deployment, even weight distribution and tow speed increase mean tow force and tow force variation about its mean. The data also show that the same ballast types should be used to access the effects of different variables because manikin and water bag ballast produce different results. Measured occupant heave acceleration was about the same as the raft heave acceleration. From occupant heave acceleration, it was estimated that after 20 hours in the raft, 20% of occupants would vomit. Formulae were proposed to predict tow force in different sea states. Mean tow forces predicted using calm water tow resistance and RAOs derived from regular wave tow tests compared well with measured mean tow force in irregular waves.Copyright